The flavour of beer is regarded as the most important quality criterion at the moment of consumption. Aroma is a key aspect of flavour and is determined by the volatile organic compounds (VOCs) present in beer. Fast and accurate analysis of these VOCs before and during beer fermentation is a growing requirement for the beer industry considering process control, quality assurance and product development.

Analytical measurement of flavour related volatiles requires specific extraction and detection techniques to obtain the necessary sensitivity and selectivity. Current techniques hamper fast evaluation of intermediate samples during the production process, which is of paramount importance for process monitoring and improved control. Selected ion flow tube-mass spectrometry (SIFT-MS) allows to instantly identify and quantify VOCs in real-time. Whether it also provides valuable data for beer flavour research, was the central question in this study. The aim of this work was to explore the high-sensitivity, real-time analysis capabilities of SIFT-MS for online monitoring of target flavour compounds in the beer production process without the need for time-consuming chromatographic separations.

From a broad range of volatiles, marker compounds associated with wort production (e.g. DMS) and beer fermentation (e.g. acetaldehyde and diacetyl) were selected for evaluation. Hyphenation of static headspace extraction of these marker compounds with SIFT-MS detection was carried out by means of a CTC CombiPAL autosampler installed on a Thermo TraceGC that is directly connected to the SIFT-MS instrument (Voice200, Syft Technologies, Christchurch, New Zealand). Hyphenation between headspace sampling and direct SIFT-MS detection was achieved by a heated external interface without any restriction installed, providing direct entry to the flow tube of the Voice200. The target compounds were analysed using selected ion mode and abundance was derived from the measured signal intensity at the specific product ion masses. Cycle time per individual sample was reduced to 5 min and the SIFT-MS analysis time to 20 s.

Our data demonstrate that quantitative real-time measurement of target compounds by SIFT-MS is of high added value for on-going brewing research, and for subsequent applications in the brewing industry, e.g. monitoring fermentation and fast evaluation of wort quality parameters. Whereas GC-MS is the technique of choice for detailed analytical volatile fingerprinting, it is not suited for real-time quantitative monitoring. In this respect, SIFT-MS technology is fully complementary to GC-MS for VOC characterisation, with enhanced productivity and more information from a single analysis as important benefits.